1. Field of the Invention
The present invention relates generally to a power fault detection system and, more particularly, to a detection system for use in conjunction with a communication bus for a marine vessel.
2. Description of the Prior Art
Many types of communication systems are known for use in conjunction with a marine vessel, in which a plurality of devices are connected to a communication bus, such as a CAN bus which is well known to those skilled in the art. Although many different types of communication buses are used in vehicle communication systems, one particularly well known system was developed and provided by Robert Bosch GmbH and that system is known as a CAN bus. It is a Controller Area Network (CAN) bus and details of the CAN protocol have been described in detail in a 1991 revision of a CAN specification, versions 1.2 and 2.0, which are very well known to those skilled in the art and will not be described in detail herein.
U.S. Pat. No. 6,273,771, which issued to Buckley et al. on Aug. 14, 2001, discloses a control system for a marine vessel. The control system incorporates a marine propulsion system that can be attached to a marine vessel and connected in signal communication with a serial communication bus and a controller. A plurality of input devices and output devices are also connected in signal communication with a communication bus and a bus axis manager, such as a CAN Kingdom network, is connected in a signal communication with the  controller to regulate the incorporation of additional devices to the plurality of devices in signal communication with the bus, whereby the controller is connected in signal communication with each of the plurality of devices on the communication bus. The input and output devices can each transmit messages to the serial communication bus for a receipt by other devices.
U.S. Pat. No. 6,382,122, which issued to Gaynor et al. on May 7, 2002, discloses a method for initializing a marine vessel control system. An auto detect system is provided for a marine vessel in which the various associations and relationships between marine vessel devices, gauges, sensors, and other components are quickly and easily determined. The system performs a method which automatically determines the number of marine propulsion devices on the marine vessel and, where needed, prompts the boat builder or marine vessel outfitter to enter various commands to identify particular marine propulsion devices with references to their location on the marine vessel and to identify certain other components, such as gauges, with reference to both their location at a particular helm station and their association with a particular marine propulsion device.
U.S. Pat. No. 5,469,150, which issued to Sitte on Nov. 21, 1995, describes a sensor actuator bus system. A four-wire bus is provided with a two-wire power bus and a two-wire signal bus and a plurality of sensors and actuators attached to both two-wire buses. A modification is provided to the standard CAN protocol developed and provided by Robert Bosch GmbH, in which the standard CAN header, of a data packet is modified to incorporate a shortened device identifier priority. By shortening the identifier field of the CAN header three bits are made available for use as a short form protocol data unit which can be used to contain binary information representing both the change of status of an identified device and the current status of the device. The same three-bit PDU can be used to  acknowledge receipt of the change of status information. In order to retain all of the beneficial capabilities of the standard CAN protocol, the three-bit short form PDU can also be used to identify the use of additional bytes of a data field so that a device can take advantage of the more complex capabilities of the standard CAN protocol. However, in situations where a mere change of status report is sufficient, the present invention reduces the length of a message from a minimum of three bytes to a length of two bytes to obtain the significant benefits of increased speed of message transmission.
U.S. Pat. No. 6,564,739, which issued to Doetsch on May 20, 2003, describes a marine steering system having dual hydraulic and electronic output. The system is operable in either power steering or manual hydraulic modes. The system employs a modified helm pump having a single rotatable input shaft connectable to a steering wheel and dual hydraulic and electronic outputs. An encoder, such as an optical incremental encoder or hall effect device, is mechanically coupled to the input shaft for generating an electronic steering control signal representative of the change in position of the steering wheel. In power steering mode, the electronic steering signal is processed by an amplifier controlling the operation of an auxiliary pump set connected to the rudder steering cylinder. A bypass manifold is disposed between the helm pump and steering cylinder and disables the hydraulic steering system in the power steering mode. In the event of power failure, the bypass manifold valves are open and the system automatically switches to manual hydraulic steering.
U.S. Pat. No. 6,587,765, which issued to Graham et al. on Jul. 1, 2003, describes an electronic control system for marine vessels. The system has one or more engines and a transmission associated with each engine includes one or more control stations, each having a control arm. The system includes one or more electronic control units, each of which is electro-mechanically coupled to an  engine and transmission. A first electronic control unit (ECU) controls a throttle of a first engine and a shift position of a first transmission based on the electrical signal. The second ECU is coupled to the first ECU via the communications link, and controls the throttle of a second engine in the shift position of a second transmission based on a control signal from the first ECU.
In certain types of marine applications of communication buses, a reliable power supply at the helm of a marine vessel is extremely important, particularly if a drive-by-wire system is being used. In other words, if the throttle control handle is not mechanically connected to the actual throttle control of the marine propulsion system and the propulsion system relies on signals to transmit the desired handle position, a loss of power in the cable can be a very serious matter. In addition, without the provision of reliable electrical power, micro processors used on drive-by-wire systems could automatically reset, lock-up, or operate erratically. It is therefore important that these types of control systems be properly installed and maintained on the marine vessel. If a fault of any kind exists in the communication bus, it would be significantly helpful if this type of fault could be immediately monitored and detected to avoid improper operation of the drive-by-wire system as a result.
Many systems monitor battery voltage and provide a warning to the operator of a marine vessel if the battery is low or, for any reason, exhibits a battery voltage that is too high. However, it would be significantly beneficial if a system could be provided that detects other sorts of fault conditions such as bad connections at various junctions of the communication bus.
The patents described above are hereby expressly incorporated by reference in the description of the present invention. 